White House press secretary Jay Carney says the president spoke briefly with Buffett and "wished him well." Buffett told shareholders in a letter released late Tuesday that his condition is "not remotely life-threatening."

Obama has called his proposal to raise taxes on millionaires the "Buffett rule." Buffett has complained that he pays a lower tax rate than his secretary, a problem he says is indicative of a lack of fairness in the tax code.